This project will be almost entirely 3D Printed. The original alien suit in the
movie was made from a combination of fiberglass and latex rubber. I attempted
a similar build to this some time ago which proved messy
and time consuming.

For this project I'll be using a
Lulzbot TAZ 3D printer.
The printer also has a dual extruder fitted which as well as having the standard
Greg's Wade Exturder, also has Lulzbot's Flexystruder. This has not yet been
relased as a product by Lulzbot, but you can get all of the CAD and source from
the Lulzbot
development site if you wish to build your own - this is know as a
FlexyDualie.

We can make multi-material prints by drawing the two parts that we want as
separate pieces, I used
Autodesk123D Design for the pieces below, which is free software. Each piece
is exported as as separate STL, and then the 'combine multi-material STL'
function is used in Slic3r to
generate the GCode to drive multiple extruders on the printer.

I've used a tall skirt on the print to help wipe off excess material from the
nozzle that's not in use when the other one is printing. The prints are fairly
clean, but I probably need to experiment with the retraction settings further to
stop the excess ooze:

Of course one part is a wheel printed with it's tire bonded to it in one print.
We could adjust the density of the print to make the tyre softer - this can be
done within the Slic3r infill settings, so we can keep the same 3D model but
change the setting to alter the print for different situation.

The other two parts are a caterpillar style track with rigid inserts to stop it
bending in the other direction. We could also extend these inserts to allow a
coupling to be made so it can be attached to itself or further sections. We
could also make rigid teeth on the inside to allow a sprocket to grip it.

The last part is a compliant joint - thinner pieces of ABS encapsulated with
Ninjaflex rubber. As with the tyre example we could use a more or less dense
infill for the rubber parts to make the joint more or less bendy - this would
have potential used in prosthetic limbs and robotics, and could easily be
customised to suit the patient in the case of prosthetics.

Of course these style of hybrid prints have many uses in costumes and props -
which intend to experiment with through the build of the Alien parts. This
costume will lend itself to the concept quite well due to the appearance of the
creature which was originally intended to be a biomechanical life form.